ACARS/VHF transceiver interface unit (AVIU)

ABSTRACT

An Aircraft Communication, Addressing, and Reporting System (ACARS) to VHF transceiver interface unit (AVIU) which allows direct pilot control of the VHF mode (voice or data) and also commands the ACARS into the proper mode.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation of application Ser. No. 08/711,385 filed Sep. 6,1996, allowed, which is a continuation of application Ser. No.08/255,594, filed Jun. 8, 1994, abandoned, which is a continuation inpart of application Ser. No. 07/975,972, filed Nov. 13, 1992, abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to multi-purpose radio systems, and moreparticularly to an interface (AVIU) between an aircraft communication,addressing and reporting system (ACARS) and VHF transceiver.

2. Problem Statement

The interface between the ARINC 724/724B Aircraft Communication,Addressing, and Reporting System (ACARS) management unit (MU) and theARINC 716 VHF transceiver includes two discrete analog signals. The portselect discrete is used by the ACARS to command the VHF radio to use theACARS-provided tuning information (Transmitted from the ACARS using adigital ARINC 429 data bus). The selection of the ACARS tuning is madewhen the radio detects a path-to-ground on the port select discrete. Thevoice/data discrete is used by the ACARS to command the VHF radio to usethe ACARS-provided audio signal when the ACARS-provided keyline is"closed." The selection of ACARS keying is made when the radio detects apath-to-ground on the voice/data discrete.

The use of ACARS discretes to control transmission and tuning in effectmakes the VHF radio an extension of the ACARS, ACARS software iscertificated to the DO-178A level 3, non-essential. ACARS is considerednon-essential equipment. The VHF radio systems are certificated asessential equipment. The connection of ACARS in the manner describedabove degrades the VHF integrity to that of ACARS, in effect making theradio(s) connected to ACARS non-essential equipment. The FAA has rulesthat a radio with an interface to ACARS, as described above, may not beused for ATC communication.

PRIOR ART PATENT LITERATURE

Voice/data communication systems are shown in U.S. Pat. Nos. 5,063,610to Alwadish and 2,795,649 to Carter. Multi-voice channels areillustrated in the patent literature in U.S. Pat. Nos. 2,616,973 toMantz; 4,551,854 to Rutty; 4,494,244 to Arndt; and 4,932,071 to Arndt.Japanese patent No. 2-13024 is illustrative of the use of two datacircuits on the same channel.

U.S. Pat. No. 5,046,130 issued to Hall, et. al. shows a device which isprimarily developed to automate the reporting of position via a radiolink. Hall, et. al. shows the utilization of a radio for both voice anddata communications. In one configuration, if the user chooses to make avoice or data transmission the system can automatically attach aposition report (either before or after the user commandedtransmission). Hall, et. al. provides for several other means oftransmitting a position report, such as in request to a received poll,or when a timer expires.

In contrast to the present invention Hall, et. al. does not address theconcerns of isolating an essential voice transmitter from failures of adata system. Hall, et. al. does not address a means to monitor andcontrol ACARS voice and data modes to ensure consistent modeannunciation's to the pilot commanded VHF transceiver voice or datamode. Hall, et. al. does not address a means to add the abovefunctionality while not modifying the existing ACARS and VHFtransceivers.

ACARS is installed to provide data communications capability. In almostall cases, the ACARS is connected to a VHF transceiver that is alreadyutilized for voice communications. Unlike Hall, et. al., there is nocase of consecutive voice and data communications over a singlefrequency. A significant feature of the present invention, the AVIU, isto allow an affected VHF transceiver to be used for essential VHF voicecommunications while at the same time providing alternate capability forACARS data communications and also while protecting the VHF voicecommunications from ACARS failures (accomplished with no internal changeto the existing ACARS or VHF system). Hall, et al does not addresssystem safety considerations.

The operator interface to the VHF system is unchanged with theinstallation of the AVIU compared to the interface prior to installationof the AVIU. There are some exceptions, when no dedicated momentarygrounding push button is installed to allow pilot command of a modechange from/to voice from/to data mode. However, the installation ofthis switch is widespread, and well known. There is nothing unique toinstallation of the switch.

The operator interface to the ACARS requires access to a control anddisplay unit (CDU). The CDU presents pages of information electronicallycontrolled by the ACARS, and allows pilot selections from these menupages. It is possible for the ACARS to have a selection in the CDU menupages that allows the pilot to choose between voice or data mode.However, this selection relies on ACARS directly controlling the voiceor data mode of the affected VHF transceiver. To protect the radio fromACARS failures, this feature is overridden by the AVIU (ACARS/VHFtransceiver interface unit). The resulting CDU menu page displays will,however, respond to the AVIU, and ultimately display the mode commandedby the AVIU. The AVIU accomplishes this without a requirement to modifythe ACARS.

It is not seen how the operator interface of Hall, et. al. is related tothe present AVIU. Hall, et. al. uses radios that are primarily used forvoice or data communications. The addition of a position report to avoice transmission could be construed as a combined voice/data radio,but only very short data transmissions are allowed in the voice radio,and the voice radio's primary purpose is for voice communications. TheVHF radio connect to an AVIU is designed to be used either for voice ordata communications, but never at the same time. The operator of Hall,et. al. device does not need to choose modes, one radio is for voice,the other for data. The present AVIU is designed primarily to allowdirect pilot control of voice or data mode of the VHF transceiver whileautomatically commanding the ACARS to voice or data mode to match.

BRIEF SUMMARY OF THE INVENTION

The ACARS/VHF Interface Unit (AVIU), according to the present invention,provides adequate partitioning between the ACARS MU and the VHFtransceiver, such that the radio may be considered for credit asessential equipment. The AVIU provides this partitioning by interruptingthe ACARS port select and voice/data discretes and the MIC keyline andaudio output signals to the radio, and providing a means of positivepilot control over these discretes and signals. Pilot command of voiceor data mode switching utilizes existing capability already provided forin either the VHF radio control panel, the VEF tuning control head, or adedicated ACARS control panel, depending on the particular installation.

While the AVIU allows for direct pilot control of the VHF mode (voice ordata), the AVIU also automatically commands the ACARS into the propermode. This is accomplished by providing a command into the ACARS remotevoice/data input. A momentary ground signal of 50 ms or more willcommand the ACARS to change either from voice to data mode or data tovoice mode. The AVIU monitors the ACARS voice/data analog discretesignal to verify that ACARS has changed to the proper mode. Also, theAVIU will command the ACARS back into the proper mode if the ACARSindependently changes mode.

The AVIU must provide control of the radio such that it is improbablethat a failure will occur which precludes the pilot from using the radiofor voice communication. The AVIU gains this level of integrity byutilization of hardware components only, with no reliance on software.This design approach provides a relatively low-cost means of compliancewith FAR 25.1309(b)(2).

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a partial schematic and block diagram of the present ACARS/VHFinterface unit (AVIU);

FIG. 2 is a block and partial schematic diagram illustrative of thepresent ACARS/VHF interface with (AVIU) showing installation as aseparate unit and

FIG. 3 is a block and partial schematic diagram of an alternative methodof interconnection which requires the present ACARS/VHF interface unit(AVIU) function to be absorbed into the ACARS itself rather than aseparate unit as the embodiment of FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION

Input Signal Conditioning 21

Cockpit Remote Voice/Data Switch 211

Turning to FIG. 1, it can be seen that a push-button switch is providedin the flight deck for use by the flight crew to command the ACARS tochange voice/data mode. This push-button, when depressed, provides apath-to-ground. The input signal conditioning on this signalaccomplished two requirements: first, the signal from the switch must be"debounced"; second, the analog open/ground state must be converted intoa logical signal with electrical characteristics consistent with thelogic circuits used throughout the AVIU.

The logically true state shall be determined only when the inputprovides a path-to-ground continuously for a minimum of 50 ms. The truestate shall be maintained until such time the signal has been determinedto be in the open state. The logically false state shall be determinedwhenever the input is not determined to be logically true.

ACARS Voice/Data Output 212

The input signal conditioning of the ACARS voice/data output shallassociate the analog signal with the correct logical state, withelectrical characteristics consistent with logic circuits usedthroughout the AVIU. The logically true state shall be determined whenthe ACARS voice/data output is determined to provide a path-to-ground.The true state, therefore, is determined when the ACARS is in data mode.The logically false state is determined when the ACARS voice/data outputis not determined to be true. The false state, therefore, is determinedto be voice mode.

ACARS 5P Processing Control 213

The input signal conditioning of the ACARS 5P processing control signalshall associate the analog signal with the correct logical state, withelectrical characteristics consistent with logic circuits usedthroughout the AVIU. The logically true state shall be determined whenthe ACARS 5P processing control signal is determined to provide apath-to-ground. If this input is left open (false), the AVIU willprovide no additional delay in switching from data to voice mode.

Toggle Flip-Flop 22

The momentary true logical state from the Cockpit Remote Voice/DataSwitch input signal conditioning hereinbefore described provides theinput to a toggle flip-flop. This flip-flop will change state when theinput is determined to a rising-edge from false to true. The flip-logoutput shall change state from either true to false, or from false totrue, depending on the initial state. The toggle flip-flop shall powerup into the true state. The true state is associated with data mode, andthe false state is associated with voice mode. The following truth tabledepicts the logical operation of the toggle flip-flop:

    ______________________________________    INPUT.sub.N-1             INPUT.sub.N OUTPUT.sub.N                                   OUTPUT.sub.N+1    ______________________________________    F        F           F         F    F        F           T         T    F        T           F         T    F        T           T         F    T        F           F         F    T        F           T         T    T        T           F         F    T        T           T         T    ______________________________________     N-1 is the past state     N is the current state     N+1 is the next state

Voice/Data Mode Logic 23

Logical Inverter 231

This inverter shall convert the output from the toggle flip-flophereinbefore described into its logically complemented state. If theoutput of the flip-flop is true, then the inverter shall provide a falsesignal. If the output of the flip-flop is false, then the inverter shallprovide a logically true signal. If the flip-flop has complementedoutputs available, then this inverter is not required. The output ofthis inverter shall be associated with the data mode when false, and thevoice mode when true.

2500 ms One-Shot 232

When the output of the Inverter changes from a false state to a truestate (data to voice mode), this logic circuit will output a true signalfor 2500 ms. This duration may not be retriggered during the 2500 mstrue state (additional false to true input state transitions will notextend the duration of the output true state).

This circuit will limit the time provided for the ACARS to transmit the5P data message when transitioning from data to voice mode. The 2500 msallows for a 100 ms command to the ACARS to change mode, 400 ms for theACARS to process the mode change command, and 2000 ms for the ACARS tosend the 5P message.

Logical Inverter and Delay 233

These inverters convert the output of the inverter, back to the samelogical sense as output from the toggle flip-flop. The output of theseinverters may be associated to the data mode while true, and the voicemode while false.

These inverters provide transport delay to account for the time toprocess through the 2500 ms one-shot. The number of inverters isselected to accommodate the required logical processing and to ensurethat the output from the inverters goes to the false state only afterthe output from the 2500 ms one-shot, has settled into the true state.

AND Gate 234

The AND gate provides a true output when both inputs are true. This gateis used to delay the transition from data mode to voice mode if 5Pprocessing is desired. The delay lasts while the ACARS 5P processingcontrol signal is true for a period of not longer than 2500 ms (asdetermined by the 2500 ms one-shot).

The delay may be shortened by detection of a false output. This willoccur when ACARS successfully transmits the 5P message prior to 2500 mselapsing since the transition from data mode to voice mode is commanded.

If 5P processing is not enabled, as described in paragraph 213, then theoutput of this gate provides no delay in transitions form data mode tovoice mode.

OR Gate 235

The OR gate provides a true output while either or both inputs are inthe true state. While the AND gate output is false, this OR gate willreflect the output as commanded by the toggle flip-flop and delayed bythe transport through the Inverters.

If 5P processing is desired, the output of the AND gate is used to holdup the output of the OR gate and effectively delay the transition fromdata mode to voice mode.

Signal Switches 236

The logically true output of the OR gate shall close six independentswitches. Each switch shall be capable of carrying either the MICKeyline or the AUDIO output signals from either one or two ACARSmanagement units. If the OR gate is logically false, the six switchesshall all open up, presenting a minimum of 100,000 ohms of resistancebetween the contacts.

These switches shall provide additional isolation between the ACARS andthe VHF radio.

ACARS Mode Change Command Logic 24

Exclusive OR 241

An exclusive OR gate is true only while either input is true, but notwhile both inputs are true. In effect, an exclusive OR is true onlywhile both inputs are in different states. This exclusive OR gatecompares the output of the toggle flip-flop to the ACARS voice/dataoutput processed. The output of this exclusive OR is true only while thetoggle flip-flop is commanding data mode and ACARS is commanding voicemode, or while the toggle flip-flop is commanding voice mode and theACARS is commanding data mode.

AND Gate 242

The AND gate is true only while all three inputs are true. As long asthe AVIU determines there is a mode disagreement, the AND gate willprovide a true pulse every 500 ms, except for the 2500 ms aftertransition from data to voice mode.

Inverter 243

This Inverter provides the logically complemented output of the 500 msone-shot. If this one-shot provides a complemented output, it may beused in place of this Inverter. This signal is used to provide 500 msspacing between mode change commands to the ACARS. The 500 ms accountsfor a 100 ms command to the ACARS, and 400 ms processing time for theACARS outputs, to reflect the mode change command. The processing timemust be considered to preclude inadvertently commanding ACARS modechanges while ACARS is still processing a mode change. This could causecontinuous and never-ending ACARS mode changes.

Inverter and Delay 244

These inverters convert the output from the 2500 ms one-shot to thelogically complemented state. If the 2500 ms one-shot provides thecomplemented output, then one of the inverters may be deleted. Theadditional inverters are provided for transport delay.

While the logic in 23 is transitioning from data to voice, care must betaken to not provide too many mode change commands to the ACARS.Specifically, the logic in 23 may delay the transition to voice mode forup to 2500 ms after commanded by the pilot. These inverters provide aninhibit, such that only one mode change command is sent to the ACARSduring the 2500 ms delay. Without this, it would be possible toinadvertently command the ACARS first to voice mode, then to data mode,and so on.

The transport delay is required to allow processing through gates 241,242, and 243 prior to the processing through the 2500 ms one-shot 232;otherwise, the initial mode change command could be inhibited. Thenumber of inverters is selected to ensure the processing of the signalthrough the 2500 ms one-shot occur after the processing through theexclusive ORs and the OR gates 241, 242, and 243, and may be adjusted inconsideration of the particular logic circuits selected.

500 ms One-Shot 245

When the output of the AND gate changes from a false state to a truestate (detecting mode disagreement between the AVIU and the ACARS), thislogic circuit will output a true signal for 500 ms. This duration maynot be retriggered during the 500 ms true state (additional false totrue input state transitions will not extend the duration of the outputtrue state). This one-shot will provide spacing between mode changecommands to the ACARS to provide for ACARS processing.

100 ms One-Shot 246

When the output of the 500s one-shot changes from a false state to atrue state, this logic circuit will output a true signal for 100 ms.This duration may not be retriggered during the 100 ms true state(additional false to true input state transitions will not extend theduration of the output true state). This one-shot will provide thelogical mode change command to the ACARS of a long enough duration toensure ACARS will respond to it.

Output Signal Conditioning 25

VHF Mode Command 251

The output of the OR gate shall be converted into an analog signalappropriate to control the VHF radio and to provide a cockpit indicationof data mode. In addition, this output is provided directly to the ACARSto assist the ACARS in controlling to the same mode as the VHF radio iscommanded. The logically true state (data mode) shall provide a path toground capable of sinking 1 amp of current at 28 VDC. The logicallyfalse state (voice mode) shall provide greater than 100,000 ohms ofresistance to ground. The transient characteristics of the analog signalshall provide no greater than 5 ms of rise or fall time to the commandedstate.

ACARS Mode Change Command 252

The output from the 100 ms one-shot shall be converted into an analogsignal appropriate to control the ACARS remote voice/data input. Thelogically true state shall provide a path-to-ground capable of sinking 1amp of current at 28 VDC. The logically false state shall providegreater than 100,000 ohms of resistance to ground. The transientcharacteristics of the analog signal shall provide no greater than 5 msrise or fall time to the commanded state.

Power Supply 30

The AVIU shall operate from 28 VDC. Normally, this power shall beprovided through the center VHF 28 VDC circuit breaker. If the AVIU isused to control either the center or the right VHF radio, then the AVIUshall accept power through both the center VHF 28 VDC circuit breakerand the right VHF 28 VDC circuit breaker. In this case, the AVIU shallbe provided power through the right VHF 28 VDC circuit breaker only whenpower is not available through the center VHF 28 VDC circuit breaker.The switching between the two power sources may be accomplished eitherexternally to the AVIU or internally to the AVIU. Sufficient capacityshall be provided to allow for continued operation throughout themomentary loss of input power of a minimum of 200 ms. Total loss ofpower shall ultimately cause all outputs to assume the open state.

Electromagnetic emissions of the AVIU shall comply with DO-160Cguidelines for essential equipment.

Failure Detection 40

Wherever possible, failure of the AVIU shall be detected, and alloutputs shall be driven to the open state.

Dual VHF Connection 50

The use of the existing ACARS/VHF switching module allows for a singleAVIU to control either radio.

Dual ACARS Connection 60

The use of the existing ACARS/VHF switching module allows for a singleAVIU to control the master ACARS. Only the ACARS intersystem bus canensure the standby ACARS assumes the proper state. However, once thestandby ACARS is made active, the AVIU will automatically command it tothe compliant mode.

ACARS-Initiated Mode Change 70

Only pilot initiate mode changes using the cockpit-provided push-buttonwill cause the AVIU to change the mode the radio is commanded to. If theACARS attempts to change the mode, either through pilot MCDU action,automatically, or by failure, the AVIU will immediately attempt tocommand the ACARS back into the proper mode. The AVIU will not changethe commanded VHF radio mode in reaction to ACARS-initiated modechanges. If the pilot elects to attempt to directly command the ACARSinto a new mode, the AVIU action will defeat the pilot action. Thispilot will have to be trained to utilize only the dedicated cockpitpush-button for mode changes.

Installation Considerations 80

The AVIU is envisioned to be a small encapsulated module that requiresonly passive cooling. This module will be bolted onto the aircraftstructure nearby the ACARS MU LRU electrical connector. All of thelogical signals required are found at the ACARS MU LRU connector. Thepower wires will have to be separately routed.

The installation provides for external strapping the ACARS 5P processingcontrol signal, if it is desired to be enabled. Left unconnected, thedelay in transitioning from data to voice mode will be eliminated.

FIG. 2

A representative installation of the AVIU is shown in FIG. 2. Thisconfiguration utilizes an AVIU that is installed as a separate unit. TheAVIU intercepts the existing wiring between an existing ACARS and VHFradio as shown.

The ACARS utilizes a software process (1) to determine whether to be invoice or data mode. A means to change mode involves inputs to thisprocess from either the ACARS remote voice data input, or through pilotselections on ACARS menus displayed on the external control and displayunit. Functionally, the ACARS implements a flip flop (2), alternativelyswitching between voice and data mode, based on these inputs.

The ACARS audio output provides modulated data to be transmitted by theVHF transceiver. The ACARS data keyline is set when the ACARS audio datais to be transmitted by the VHF transceiver. The ACARS voice data outputis set to indicate the current mode of the ACARS.

The AVIU intercepts the ACARS audio and keyline outputs and isolatesthem from the VHF radio when the AVIU is in voice mode (3). The AVIUtoggles between voice and data mode whenever the cockpit voice dataswitch is selected (4). The AVIU monitors the ACARS voice data outputand compares it to the VHF mode commanded by the AVIU (5). If the ACARSmode disagrees with the VHF mode, the AVIU provides a stimulus on theACARS voice data input to cause the ACARS to change mode. The AVIU willrespond to a disagreement between the ACARS and the VHF radio wheneverit is detected.

The VHF radio has a separate cockpit audio and keyline input providedfor transmission of pilot voice communications. The VHF radio shouldselect the ACARS audio and keyline inputs only when the AVIU providedvoice data input to the VHF radio indicates data mode. When the AVIU iscommanding voice, mode, the VHF transceiver should utilize the cockpitaudio and keyline inputs (6).

The VHF transceiver has two sources of frequency tuning information, thecockpit and the ACARS. The VHF transceiver selects the ACARS frequencysource only when the VHF port select input is set (7).

The AVIU voice data input to the VHF transceiver is also utilized toannunciate the mode of operation in the cockpit (8).

FIG. 3

An alternative method of interconnection, shown in FIG. 3, requires theAVIU function to be absorbed into the ACARS itself, rather than aseparate unit. This method allows simply replacing the ACARS tointroduce the AVIU function, rather than the installation of new,separate unit. In this configuration, the same interconnections aremade, except the ACARS encompasses the AVIU function as well.

The AVIU function is identified within the dashed line block showninside ACARS. In this configuration, the toggle flip flop (1) togglesbetween voice and data mode in response to commands from the cockpitvoice data switch. The ACARS audio and keyline inputs are isolated whilein voice mode (2). These functions, and the interface with the VHF radioare identical whether implemented as shown in FIG. 2 or FIG. 3.

In the configuration shown in FIG. 3, the ACARS is itself new.Therefore, rather than implementing the ACARS monitor function, theACARS software process (4) can be modified to recognize the voice datamode commands from the AVIU toggle flip flop (1) directly. The pilot canno longer select voice or data mode through the control and displayunit, and therefore this interface is not required.

From the proceeding, it can be seen that the present ACARS/VHFtransceiver interface unit (AVIU) provides for operator control of theVHF transceiver mode of operation based on operator comments to thecockpit voice/data switch. The VHF transceiver is normally used in voicemode, for pilot air-ground communications, but can also be used in datamode, for ACARS data communications. The present system also providesfor automatically commanding ACARS mode of operation to coincide withpilot commanded mode of the VHF transceiver. While the ACARS is capableof data communications only in data mode, it can be put into voice modewhereby the ACARS data communications are suspended until ACARS isreturned to data mode. This system provides reliable and safe VHF voicecommunication for Air Traffic Control despite any ACARS malfunction,while alternatively allowing ACARS data communications. The present AVIUalso provides a means for monitoring the ACARS voice data mode.

I claim:
 1. In combination:an aircraft communication, addressing, andreporting system (ACARS); said aircraft communication, addressing andreporting system providing port select, voice/data, MIC keyline, andaudio output representative signals; a VHF transceiver; an interfaceunit coupled between said aircraft communication, addressing andreporting system, and said VHF transceiver; said interface unitincluding means for isolating said port select, voice/data, MIC keyline,and audio output representative signals between the said aircraftcommunication, addressing and reporting system and said VHF transceiver;to allow the VHF transceiver to be utilized for safety of flight voicecommunications and for data communications in an exclusive manner.
 2. Incombination:an aircraft communication, addressing and reporting system;a VHF transceiver; a cockpit voice/data switch; an interface unitcoupled between said aircraft communication, addressing and reportingsystem, said cockpit voice/data switch, and said VHF transceiver; saidinterface unit including means for the operator control of said cockpitvoice/data switch to provide control of the VHF transceiver mode ofoperation to allow the VHF transceiver to be utilized for safety offlight voice communications and for data communications in an exclusivemanner.